It is a singular circumstance that reciprocal crosses are not always or even often possible; thus, one rhododendron may afford pollen perfectly potent on the stigma of another kind, by the pollen of which latter its own stigma is unaffected.

Similar interGlacial deposits in Tirol contain leaves of Rhododendron ponticum.

As we pass to the west the species of rhododendron, oak and Magnolia are much reduced in number as compared to the eastern region, and both the Malayan and Japanese forms are much less common.

During the milder interglacial period some southern types, such as Rhododendron ponticum, still held their own, but ultimately succumbed.

In the eastern forests the prevalence of Magnoliaceae and of Clethra and Rhododendron continues the alliance with eastern Asia.

The forest extends, with great luxuriance, to an elevation of 12,000 ft., above which the sub-alpine region may be said to begin, in which rhododendron scrub often covers the ground up to 13,000 or 14,000 ft.

But the chief ornament of Lebanon is the Rhododendron ponticum, with its brilliant purple flower clusters; a peculiar evergreen, Vinca libanotica, also adds beauty to this zone.

Laurel, rhododendron, and whortleberry are common shrubs in the mountain districts, and sumac, hazel, sassafras and elder are quite widely distributed elsewhere.

The holly, the yew, the laurel, if allowed to grow from a single stem, become trees, other plants such as rhododendron, syringa, the euonymous are properly shrubs.

Three species of rhododendron vie with each other in the brilliancy of their masses of red or pink flowers; the common juniper rises higher still, along with three species of bilberry; and several dwarf willows attain nearly to the utmost limit of vegetation.

The peach, horse-chestnut, lilac, morello cherry, black currant, rhododendron and many other trees and shrubs develop flower-buds for the next season speedily after blossoming, and these may be stimulated into premature growth.

For commercial purposes, crowns of lily of the valley, tulip and other bulbs, and such deciduous woody plants as lilac and deciduous species of rhododendron, while in a state of rest, are packed in wet moss and introduced into coldstorage chambers, where they may be kept in a state of quiescence, if desired, throughout the following summer.

These causes of change in phyllotaxis are also well exemplified in the alteration of an opposite or verticillate arrangement to an alternate, and vice versa; thus the effect of interruption of growth, in causing alternate leaves to become opposite and verticillate, can be distinctly shown in Rhododendron ponticum.

Growing under the shade of these are several varieties of rose, honeysuckle, currant, gooseberry, hawthorn, rhododendron and a luxuriant herbage, among which the ranunculus family is important for frequency and number of genera.

A great variety of shrubs grow on these slopes of the western Caucasus, chiefly the following species, several of which are indigenous - Rhododendron ponticum, Azalea pontica, Aristotelia maqui, Agave between 1864 and 1878, and the country where they had lived remained for the most part unoccupied until after the beginning of the 10th century.

The alpine rose (Rhododendron dauricum) clusters in masses on the higher mountains; juniper, spiraea, sorbus, the pseudo-acacia (Caragana sibirica and C. arborescens, C. jubata in some of the higher tracts), various Rosaceae - Potentilla fruticosa and Cotoneaster uniflora - the wild cherry (Prunus Padus), and many other shrubs occupy the spaces between the trees.

The outer ranges of mountains are mainly covered with forests of Pinus longifolia, rhododendron, oak and Pieris.